Effect of hexagonal WO3 morphology on NH3 sensing

Tungsten oxide nano - powders were prepared by acidic precipitation from so dium tungstate solution. The alternative processes of the applied hydrothermal method resulted in different structure and morphology of hexagonal WO 3 nano - crystals. Micro - hotplates wi th gold electrodes on top to measure sensing layer conductivity were fabricated. WO 3 layers of the two morphologies were depos ited using capillary dropping technique. Sensor responses were measured up to 22 0 °C operation temperature for NH 3 diluted in synthetic air in the 10 - 100 ppm range. Test results are compared in terms of conductivity, sensitivity and response time

Investigation of Combinatorial WO3-MoO3 Mixed Layers by Spectroscopic Ellipsometry using Different Optical Models

Reactive (Ar-O2 plasma) magnetron sputtered WO3 -MoO3 (nanometer scaled) mixed layers were investigated and mapped by Spectroscopic Ellipsometry (SE). The W- and Mo-targets were placed separately, and 30 × 30 cm glass substrates were slowly moved under the two (W and Mo) separated targets. We used different (oscillator- and Effective Medium Approximation, EMAbased) optical models to obtain the thickness and composition maps of the sample layer relatively quickly and in a cost-effective and contactless way. In addition, we used Rutherford Backscattering Spectrometry to check the SE results. Herein, we compare the “goodness” of different optical models depending upon the sample preparation conditions, for instance, the speed and cycle number of the substrate motion. Finally, we can choose between appropriate optical models (2-Tauc-Lorentz oscillator model vs. the Bruggeman Effective Medium Approximation, BEMA) depending on the process parameters. If one has more than one “molecular layer” in the “sublayers”, BEMA can be used. If one has an atomic mixture, the multiple oscillator model is better (more precise) for this type of layer structure

Sensing Layer for Ni Detection in Water Created by Immobilization of Bioengineered Flagellar Nanotubes on Gold Surfaces

The environmental monitoring of Ni is targeted at a threshold limit value of 0.34 mu M, as set by the World Health Organization. This sensitivity target can usually only be met by time-consuming and expensive laboratory measurements. There is a need for inexpensive, field-applicable methods, even if they are only used for signaling the necessity of a more accurate laboratory investigation. In this work, bioengineered, protein-based sensing layers were developed for Ni detection in water. Two bacterial Ni-binding flagellin variants were fabricated using genetic engineering, and their applicability as Ni-sensitive biochip coatings was tested. Nanotubes of mutant flagellins were built by in vitro polymerization. A large surface density of the nanotubes on the sensor surface was achieved by covalent immobilization chemistry based on a dithiobis(succimidyl propionate) cross-linking method. The formation and density of the sensing layer was monitored and verified by spectroscopic ellipsometry and atomic force microscopy. Cyclic voltammetry (CV) measurements revealed a Ni sensitivity below 1 mu M. It was also shown that, even after two months of storage, the used sensors can be regenerated and reused by rinsing in a 10 mM solution of ethylenediaminetetraacetic acid at room temperature

Ionsugaras módszerek a fizikai nanotechnológiában (IONNANO) = Ion beam modifications in near-to-physics nanotechnology

Témavezeto: Gyulai József - SiO2 mátrixban Si, Pd-Pt és SiC, valamint SiC-ben gyémánt nanokristályokat állítottunk elő és minősítettünk. - Szén nanocsöveket Ar+ ionokkal besugározva, ponthibákat, kiemelkedő klasztereket és szuperstrukturákat figyeltünk meg. - Ellipszometriával mértük a szilíciumkarbidban ionimplantációval létrejövő roncsoltságot. - Az ionsugaras kutatásaink alapján eljárást fejlesztettünk ki, amellyel külön-külön detektálható a Si-, valamint a C-alrács károsodása. - Ezzel sikerült megbecsülni a He ion c-tengelyi csatorna irányú és random irányú energiaveszteség arányát. - Optikai modelleket fejlesztettünk ferroelektromos anyagok mérésére, valamint továbbfejlesztettük a rácskárosodás ellipszometriai modelljét. - Extrém kis energiájú ionok folyamatainak kutatása a porlasztást alkalmazó felületvizsgáló módszerek kvantifikálását célozta: - új ionkeveredési mechanizmust javaslunk birétegekre - Molekula-dinamikai szimulációnkat kiterjesztettük több ion szukcesszív becsapódásának a vizsgálatára a Ti/Pt kettősrétegben. - Súrlódó beesésnél a szén porlasztási sebessége nagyobb, mint a fémeké. - Kerámiák nanoszerkezetének módosítása témában kiemelkedő eredményünknek tartjuk, hogy a világon elsőként nekünk sikerült előállítani karbon nanocső - szilícium-nitrid kompozitot, amelyben a nanocsövek nem degradálódnak a szinterelés során. | Principal investigator: Gyulai József - Nanocrystals were prepared and characterized: Si in SiO2, Pd-Pt, SiC in Si, and diamond in SiC. - Argon ion irradiation of carbon nanotubes resulted in point defects, clusters and superstructures, as detected with atomic resolution AFM. - Ellipsometry proved itself as efficient method to study radiation damage in SiC. - New version of ion beam analysis applied to implanted SiC allowed us to detect the damage of the carbon and silicon sublattice separately - With defects as markers, ratio of channeled to random stopping power of He ions could be deduced. - Optical model was developed for ellipsometry allowing also characterization of ferroelectric (high-k) materials. - Modeling and experimental studies of damaging and sputtering processes at impact of extreme low-energy resulted in better quantification of surface analysis techniques (Auger profiling): - MC simulation of bilayers led us to a new model of ion beam mixing. - MD simulations were extended to multiple ion impact on Ti/Pt bilayers. - Sputtering coefficient of carbon was found (and modeled) to be higher than that of a metal for sputtering at glancing angle incidence. - Nanostructure of ceramic materials, firstly, of Si3N4, resulted in the first Si3N4-carbon nanotube nanocomposite, where the nanotubes will not degrade during high-temperature sintering

Együtt-párologtatott négykomponensű félvezető vékonyréteg fotovoltaikus célra = Co-evaporated four-component semiconductor thin films for photovoltaics

A CIGS PV szerkezet kutatásának célja az együtt-párologtatásos előállításnál fellépő folyamatok megismerése; és az n-típusú puffer-réteg létrehozása vákuumtechnikailag zárt ciklusba rendezhető módon. Utóbbit az atomi réteg-leválasztási technika hazai bevezetésével oldottuk meg. Kb. 200 ciklusban Zn-és 2 at% Al prekurzor-technikával Al-mal adalékolt ZnO-rétegek üveg hordozón T= 210-220°C-on reprodukálhatóan kialakíthatók n=1,2•1021cm-3 adalékkoncentrációval, µ= 0.7 cm2/Vs mozgékonysággal ill. ρ≈2 mΩcm (1 ill. 7 mΩcm laterális és normális) vezetőképességgel. A CIGS rétegnövesztést ún. flash-párologtatásos módszerrel és utólagos szelenizációval vizsgáltuk. Ampullában, együttes párologtatással (T=500°C, t=15min) csak kalkopirit összetevők mutathatók ki, a hőkezelés csak a Ga-tartalmat befolyásolja. Az ideális CuIn0,8Ga0,2Se2 összetétel 10-15 perces hőkezeléssel beállítható a szokásos morfológiával, amit konformálisan fed be a kb. 40nm ALD pufferréteg . Üvegen, Mo-elektródra párologtatott (In, Ga) és porlasztott (Cu) fémösszetevők rétegsorrendjének szerepe döntő utólagosan szelenizált rétegszerkezeten. Felpárologtatott Se-forrás hőkezelésével (változó gőznyomáson) vákuumban a szelenizáció nem sikeres, de konstans gőznyomáson (ampullában) tökéletes, ha a fémrétegek sorrendje In, Ga, Cu. | The research on CuInGaSe2 (CIGS) thin film PV structures aimed at understanding of fundamental phenomena at the co-evaporation of the absorber layer; and the development of n-type buffer-layer by an integrable vacuum-method. Latter problem was solved by the adoption of the Atomic Layer Deposition (ALD) technique. In ca. 200 cycles of alternating Zn and ca. 2at% Al precursor pulses Al-doped ZnO layers on glass substrates could be formed reliably at T= 210-220°C with n=1,2•1021cm-3 doping concentration, µ= 0.7 cm2/Vs mobility and ρ≈2 mΩcm (1 vs. 7 mΩcm lateral and normal) resistivity. CIGS layer growth by the "flash-evaporation" method and with the post-selenisation of the metallic precursors was studied. Co-evaporation at T=500°C, t=15min results in solely chalcopyrite components, annealing time affects only the Ga-content in the layer. The composition CuIn0,8Ga0,2Se2 ideal for PV application can be set by an annealing for 10-15 min with the usual morphology, to be covered conformally by the ca. 40nm ALD buffer. The influence of the sequence of evaporated (In, Ga) and sputtered (Cu) metallic components on Mo-coated glass was studied by structural analyses on post-selenized d= 800…1200 nm layers. By the annealing of evaporated Se-source on top in vacuum (i.e. at varying Se vapour pressure) selenization was not successful. At constant vapour pressure (ampoule method) with a metal-layer order of In, Ga, Cu selenization is perfect

Compositional Optimization of Sputtered WO3/MoO3 Films for High Coloration Efficiency

Thin films of mixed MoO3 and WO3 were obtained using reactive magnetron sputtering onto ITO-covered glass, and the optimal composition was determined for the best electrochromic (EC) properties. A combinatorial material synthesis approach was applied throughout the deposition experiments, and the samples represented the full composition range of the binary MoO3/WO3 system. The electrochromic characteristics of the mixed oxide films were determined with simultaneous measurement of layer transmittance and applied electric current through the using organic propylene carbonate electrolyte cells in a conventional three-electrode configuration. Coloration efficiency data evaluated from the primary data plotted against the composition displayed a characteristic maximum at around 60% MoO3. Our combinatorial approach allows the localization of the maximum at 5% accuracy

Investigation of Electrochromic, Combinatorial TiO₂-SnO₂ Mixed Layers by Spectroscopic Ellipsometry Using Different Optical Models

We determined the optimal composition of reactive magnetron-sputtered mixed layers of Titanium oxide and Tin oxide (TiO2-SnO2) for electrochromic purposes. We determined and mapped the composition and optical parameters using Spectroscopic Ellipsometry (SE). Ti and Sn targets were put separately from each other, and the Si-wafers on a glass substrate (30 cm × 30 cm) were moved under the two separated targets (Ti and Sn) in a reactive Argon-Oxygen (Ar-O2) gas mixture. Different optical models, such as the Bruggeman Effective Medium Approximation (BEMA) or the 2-Tauc–Lorentz multiple oscillator model (2T–L), were used to obtain the thickness and composition maps of the sample. Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) has been used to check the SE results. The performance of diverse optical models has been compared. We show that in the case of molecular-level mixed layers, 2T–L is better than EMA. The electrochromic effectiveness (the change of light absorption for the same electric charge) of mixed metal oxides (TiO2-SnO2) that are deposited by reactive sputtering has been mapped too

Compositional Optimization of Sputtered WO₃/MoO₃ Films for High Coloration Efficiency

Thin films of mixed MoO3 and WO3 were obtained using reactive magnetron sputtering onto ITO-covered glass, and the optimal composition was determined for the best electrochromic (EC) properties. A combinatorial material synthesis approach was applied throughout the deposition experiments, and the samples represented the full composition range of the binary MoO3/WO3 system. The electrochromic characteristics of the mixed oxide films were determined with simultaneous measurement of layer transmittance and applied electric current through the using organic propylene carbonate electrolyte cells in a conventional three-electrode configuration. Coloration efficiency data evaluated from the primary data plotted against the composition displayed a characteristic maximum at around 60% MoO3. Our combinatorial approach allows the localization of the maximum at 5% accuracy

Ellipsometry monitoring of sensor processes based on gold nanoparticle bonded proteins

The aim of our work is to develop a heavy metal detection sensor that can be used in the field to easily and accurately test water samples at the range of the strict concentration levels set by international standards. The sensor is based on a gold thin-film electrode on a silicon substrate and a genetically modified bacterial flagellin protein deposited onto the gold thin-film electrode. To ensure that the surface is adequately covered, and the protein is attached to the electrode, additional gold nanoparticles were deposited to the surface. Changes on the sensor surface were investigated by in-situ ellipsometry and cyclic voltammetry. The determination of the exact surface morphology, as well as the validation of the ellipsometric measurements were done by using scanning electron microscope